1. Field
Although not so limited in its utility or scope, implementations and embodiments of the present invention relate to the fabrication and structures of illuminable image-transporting optical fiber bundles.
2. Brief Description of Illustrative Environments and Related Art
Illuminable image-transporting optical fiber bundles are well-known to practitioners in the field of optical-fiber component fabrication. Generally, such an illuminable image-transporting bundle includes a first, typically inner bundle of fused or otherwise adjacently and rigidly bonded optical fibers that combine to form an image conduit for transporting an image between coherently arranged first and second image-bundle ends. The image bundle may be rigid throughout its length or include a central flexible region as is known to those in the related art; a key aspect, however, is retaining the ends of the individual optical fibers included in the image bundle in fixed relative positions in order to maintain image integrity between the image-input and image-output ends. A second, typically outer bundle or “branch” of light-conducting fibers conducts light from a remote source and projects that light onto objects the images of which are introduced into the image-input end of the imaging portion of the overall optical fiber bundle assembly.
Although the scope of the present invention is not limited to illuminable image-transporting fiber bundles, representative examples of how, traditionally, such fiber bundles are fabricated informs an appreciation for more general aspects of the invention. An early, and still relevant, “method of fabricating illuminated fiber optics” is described in U.S. Pat. No. 3,674,452 issued in the name of R. R. Strack on Jul. 4, 1972 (hereinafter the '452 patent), major aspects of which are described below in conjunction with FIGS. 1A-1D. According to the method of the '452 patent, the fabrication of a branched fiber optic viewing device adapted to conduct illuminating light to objects to be viewed thereby through one branch of the device and simultaneously transport images of the illuminated objects to a remote viewing location through another branch of the device is initiated by positioning a multiplicity of light-transmitting optical fibers in parallel side-by-side relationship with each other as a bundle having opposite ends of said fibers disposed in identical geometrical patterns at corresponding opposite ends of the bundle, the fibers each having an outer, leachable cladding of silica-free acid soluble glass. The fibers are then fused together along the full length of the bundle, such as by heating and drawing in an optical fiber drawing tower, to yield a fused optical fiber bundle such as the illustrative bundle of FIG. 1A. As shown in FIG. 1B, a selected set of outermost fibers of the bundle adjacent one end of the bundle is cut back (e.g., machined) in order to shorten the selected outermost fibers and expose cut-back ends thereof intermediately of the length of the bundle. Referring to FIG. 1C, the ends of the remaining (i.e., non-cut) fibers at the end of the bundle from which the selected fibers were cut are masked with, for example, an acid-resistant coating material, and the opposite, non-cut end of the bundle is similarly masked. Once masked, the bundle is immersed in an acidic solvent (not shown) in order to leach the outer claddings of silica-free glass away from all uncovered portions of all fibers and render each fiber independently flexible and to free the exposed cut-back ends of the outermost fibers from each other and from adjacent other fibers of the bundle. A selected set of the freed cut-back ends of the outermost fibers is then gathered together as a group adjacent one side of the remaining fibers of said bundle whereby said gathered-together outermost fibers comprise said one branch (e.g., an illuminating branch) of the device for receiving and conducting light to objects intended for viewing by the branched fiber optic viewing device, as shown in FIG. 1D.
While the basic principles taught by Strack in the '452 patent remain among the standards for the fabrication of illuminable image-transporting fiber bundles, disadvantages accompany the method taught in the '452 patent and other, similar methods. For instance, the machining away of a section of the fused bundle extending axially and, in the case of a cylindrical bundle, radially inwardly in order to cut back selected outer fibers for ultimate use as flexible illuminating fibers can damage (e.g., shatter and splinter) several layers of both outer illuminating and inner imaging fibers, rendering such fibers unusable for their intended purposes. Moreover, general handling of the fused bundle in preparation for, and execution of, steps subsequent to its initial formation sometimes results in physical damage to exterior fibers. In addition to the aforementioned machining performed in preparation for masking and leaching, the unleached end of a fiber bundle of the general type previously described is sometimes machined in order to configure it for cooperative engagement with a housing, coupling or another optical component, such as a lens. For instance, in one alternative configuration, the fused ends of illuminating optical fibers are machined away so that the imaging fibers terminate at an image-input face and the illuminating fibers terminate at a peripheral light-emission face that is recessed with respect to the image-input face. In alternative aspects, end portions of the imaging fibers are machined away to form an image-input face that it recessed with respect to the peripheral light-emission face to form a channel into which, for example, one or more optical elements (e.g., a lens) is mounted for focusing an image onto the image-input face. It will be appreciated that machining for the latter purposes subjects the fused bundle to the same risk of fiber damage previously described in connection with preparing the fused bundle for leaching.
Accordingly, there exists a need for a fused bundle configuration that can be handled and machined with a minimized risk of damage to constituent optical fibers of the imaging or illuminating varieties.